A recent paper (Terbeck, 2012) showed that, in a randomized, double-blind, placebo controlled study of 36 white university students (a typical source for participants in these sorts of studies!) were given a single dose of 40 mg. of propranolol, a beta-adrenoceptor antagonist (beta blocker) and their racial bias determined by the IAT (implicit association task). The IAT assesses implicit racial prejudice (the physical expression of prejudice) by an “item sorting task” to distinguish that from explicit racial prejudice, which is limited to what the subject thinks. Explicit racial prejudice was assessed by subjects indicating how “warm” they felt toward various racial groups.

Propranolol is a widely used medication in hypertension and other conditions in which an overactive sympathetic (adrenergic) nervous system is involved.